Sorry if this is too rudimentary: but if a single Male PR age 30+ (working professional) recieve approval of citizenship application on eocnomic terms, will he be expected to do the 2 years national service afterwards?

If so, how will this work? Does he just get a notice from the gov one day and had to quit his job and spend 2 years in jungle?

What is receiving PR on economic (I am assuming that is what you meant) terms? I'm only aware of getting PR via PTS scheme (Professional/Technical) or Family Ties. If you were approved on the PTS scheme you will not be required to do NS. If you were approved on the Family Ties scheme, you ARE liable for NS but if you are over 30 you will normally register for NS and then receive a waiver. Under either scheme, should you get married and have a male offspring, they will have to do NS as a 2nd Gen PR.

However, with some of the PRs I've seen in recent years, a 2 year stint in the jungle might well do 'em some good!